First off I figure I would just say this is not a rant about wanting EB on BI/1.3, insteadof 1., I'm looking forward to the 1.2 version.
However the single most important reason for changing to the expansion is the phlanax fix. Phalanx's will actually engage head-on, and this combined with the improved battleline means that phalanx armies are not the role-overs they are in 1.2.
I think this is important for EB as a lot of units are phalanx based.